I'm wondering if it's possible to join SharePoint 2010 to SharePoint 2013 farm and then configure SharePoint 2010 to be a Search server that can crawl and search SharePoint 2013 content? Unfortunately, I currently don't have enough capacity for building such an environment. I would think that it's possible to join SharePoint 2010 to SharePoint 2013 farm. To address my concern, maybe I have to configure Federation Search, right?